Domain search for .in (or any other tld) domain results as not available in online store, but checking domain on registrar website shows it as available for registration.
There might be issue on registrar side when incorrect response code is returned from registar API server.
Find registrar log located in
Find the API response in log, it differs for different registrars. For example, it may look as follows:
Compare the result code with information in registrar API guide.
If response code is different from check on registrar website, contact registrar with output from log for further clarifications.